Slides in this set

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Properties of exchange surfaces· A large surface area, the larger the area across which a substance can diffuse, the more substance can cross the surface in a given time.· The exchange surface should be thin, the shorter the distance across which a substance has to diffuse, the less time it takes.· There must be a DIFFUSION GRADIENT, the concentration of the substance on one side of the surface must be different from the concentration on the other side so the substance can diffuse down the gradient.· Must be protected from drying out, if `wet' cells are exposed to dry air, water vapour will diffuse out of them and into the air. If too much water is lost the plasma membrane will lose its structure.…read more

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The mammalian gas exchange system Pleural membranes which secrete pleural fluid The pleural fluid Thorax provides an airtight, slippery covering that allows the Lungs lungs to inflate easily.…read more

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The lungs· The lungs have no muscles, so movement is made by muscles in the diaphragm and by the muscles between the ribs, which are the intercostal muscles.· The cells that line the path down to the lungs are adapted to remove particles from the air.· There are two main types of cells that make up the epithelial tissue that lines the trachea and bronchi. These are called ciliated cells and goblet cells.· All of these cells sit on a basement membrane. This contains fibres made from proteins the cells underneath them have secreted.· There are many cilium on each ciliated cell. Each cilium contains microtubules which help it to move.· Goblet cells produce mucus. Mucus contains glycoproteins. These have long sugar molecules attached to them. This makes the mucus sticky. Mucus lines the epithelium and traps bacteria as well as stops the cells from drying out.…read more

Slide 6

Other tissues in the airway· Cartilage- a tough tissue that helps support the walls of the trachea and bronchi. It is very strong and flexible. The rings of cartilage in the walls of the trachea help to keep it open. In the trachea it is arranged in c shape rings, in the bronchi it is less regular.· Smooth muscle- found in the walls of the trachea, bronchi and bronchioles. It contracts slowly and steadily and can remain contracted for a long period of time. It is an involuntary muscle, so we have no conscious control over it. When it contracts it narrows the airway.· Elastic fibres- found in the walls of all of the airways, even in the smallest ones. During breathing in, the alveoli expand, stretching the elastic fibres. During breathing out the fibres recoil, helping to decrease the volume inside the lungs forcing air out.…read more